Messages in this thread Patch in this message | | | Subject | Re: [patch 3/3] futex: Prevent attaching to kernel threads | From | Davidlohr Bueso <> | Date | Mon, 12 May 2014 14:59:19 -0700 |
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On Mon, 2014-05-12 at 20:45 +0000, Thomas Gleixner wrote: > We happily allow userspace to declare a random kernel thread to be the > owner of a user space PI futex. > > Found while analysing the fallout of Dave Jones syscall fuzzer. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Cc: stable@vger.kernel.org > --- > kernel/futex.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > Index: linux-2.6/kernel/futex.c > =================================================================== > --- linux-2.6.orig/kernel/futex.c > +++ linux-2.6/kernel/futex.c > @@ -682,6 +682,8 @@ static struct task_struct * futex_find_g > p = find_task_by_vpid(pid); > if (p) > get_task_struct(p); > + else > + p = NULL; > > rcu_read_unlock(); > > @@ -814,6 +816,11 @@ lookup_pi_state(u32 uval, struct futex_h > if (!p) > return -ESRCH; > > + if (!p->mm) { > + put_task_struct(p); > + return -EPERM; > + }
It might make sense to check the mm inside futex_find_get_task(), and simply never take the refcount if NULL.
Thanks, Davidlohr
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